The present invention relates to a method for optically recording and reproducing information on and from a record carrier in the form of a disk, and more particularly to a method for highly reliably reading information from minute information marks recorded at a resolution which is higher than that of an optical reproduction system.
In a conventional optical recording apparatus, the size of a recording mark is about twice the marginal size resolvable by the optical system. To explain using specified numerical values, when the wavelength of a light source was 780 nm and the numerical aperture of an objective lens was 0.55, a resolvable mark length was about 0.35 microns a mark smaller than that mark length was considered to be illegible. In a practiced apparatus, a signal from such a mark as above was so small that an approximately doubly sized (0.7 microns) mark was recorded and reproduced in consideration of an S/N of the signal.
In the field of optical microscopes, on the other hand, a method of LuRosz has been known which improves resolution of an ordinary microscope by disposing a grating in an optical system, projecting a body on the grating, disposing another grating on an image plane on which an image as a result of the projection of the grating on the body is formed, and observing an image transmitting through the latter grating. This method is, however, dedicated to constructing a microscope for forming an image of a body and needs relative movement between the latter grating and the body, failing to be applied to an optical information recording/reproducing apparatus such as an optical disk.